Battery module lithium plating reduction

ABSTRACT

A battery system includes a lithium ion battery that couples to an electrical system. The battery system also includes a battery management system that electrically couples to the lithium ion battery and controls one or more recharge parameters of the lithium ion battery. Additionally, the battery management system monitors one or more parameters of the lithium ion battery. Further, the battery management system controls the recharge parameters of the lithium ion battery based on at least one lithium plating model and the monitored parameters. Furthermore, the at least one lithium plating model indicates a relationship between the one or more parameters of the lithium ion battery and a likelihood of lithium plating occurring in the lithium ion battery.

BACKGROUND

The present disclosure generally relates to the field of batteries andbattery modules. More specifically, the present disclosure relates tocontrolling charging operations of lithium ion batteries to reduce alikelihood of lithium plating on anodes of the lithium ion batteries.

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure,which are described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be understood that these statements are to beread in this light, and not as admissions of prior art.

A vehicle that uses one or more battery systems for providing all or aportion of the motive power for the vehicle can be referred to as anxEV, where the term “xEV” is defined herein to include all of thefollowing vehicles, or any variations or combinations thereof, that useelectric power for all or a portion of their vehicular motive force. Forexample, xEVs include electric vehicles (EVs) that utilize electricpower for all motive force. As will be appreciated by those skilled inthe art, hybrid electric vehicles (HEVs), also considered xEVs, combinean internal combustion engine propulsion system and a battery-poweredelectric propulsion system, such as 48 Volt (V) or 130V systems. Theterm HEV may include any variation of a hybrid electric vehicle. Forexample, full hybrid systems (FHEVs) may provide motive and otherelectrical power to the vehicle using one or more electric motors, usingonly an internal combustion engine, or using both. In contrast, mildhybrid systems (MHEVs) disable the internal combustion engine when thevehicle is idling and utilize a battery system to continue powering theair conditioning unit, radio, or other electronics, as well as torestart the engine when propulsion is desired. The mild hybrid systemmay also apply some level of power assist, during acceleration forexample, to supplement the internal combustion engine. Mild hybrids aretypically 96V to 130V and recover braking energy through a belt or crankintegrated starter generator. Further, a micro-hybrid electric vehicle(mHEV) also uses a “Stop-Start” system similar to the mild hybrids, butthe micro-hybrid systems of a mHEV may or may not supply power assist tothe internal combustion engine and operates at a voltage below 60V. Forthe purposes of the present discussion, it should be noted that mHEVstypically do not technically use electric power provided directly to thecrankshaft or transmission for any portion of the motive force of thevehicle, but an mHEV may still be considered as an xEV since it does useelectric power to supplement a vehicle's power needs when the vehicle isidling with internal combustion engine disabled and recovers brakingenergy through an integrated starter generator. In addition, a plug-inelectric vehicle (PEV) is any vehicle that can be charged from anexternal source of electricity, such as wall sockets, and the energystored in the rechargeable battery packs drives or contributes to drivethe wheels. PEVs are a subcategory of EVs that include all-electric orbattery electric vehicles (BEVs), plug-in hybrid electric vehicles(PHEVs), and electric vehicle conversions of hybrid electric vehiclesand conventional internal combustion engine vehicles.

xEVs as described above may provide a number of advantages as comparedto more traditional gas-powered vehicles using only internal combustionengines and traditional electrical systems, which are typically 12Vsystems powered by a lead acid battery. For example, xEVs may producefewer undesirable emission products and may exhibit greater fuelefficiency as compared to traditional internal combustion vehicles and,in some cases, such xEVs may eliminate the use of gasoline entirely, asis the case of certain types of EVs or PEVs.

As technology continues to evolve, there is a need to provide improvedpower sources, particularly battery modules, for such vehicles. Forexample, the electric power used by the xEVs may be stored in lithiumion batteries. In some cases, active lithium ions within the lithium ionbatteries of xEVs may deposit on an anode of the lithium ion batteriesunder certain conditions driving a charging operation of the lithium ionbatteries. This effect is widely known as lithium plating, and thelithium plating may result in degradation of the lithium ion battery.The present disclosure is generally related to establishing dynamicparameters for charging operations to limit lithium plating on the anodeof the lithium ion battery.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of these certain embodiments and thatthese aspects are not intended to limit the scope of this disclosure.Indeed, this disclosure may encompass a variety of aspects that may notbe set forth below.

The present disclosure relates to a battery system. The battery systemincludes a lithium ion battery that couples to an electrical system. Thebattery system also includes a battery management system thatelectrically couples to the lithium ion battery and controls one or morerecharge parameters of the lithium ion battery. Additionally, thebattery management system monitors one or more parameters of the lithiumion battery. Further, the battery management system controls therecharge parameters of the lithium ion battery based on at least onelithium plating model and the monitored parameters. Furthermore, the atleast one lithium plating model indicates a relationship between the oneor more parameters of the lithium ion battery and a likelihood oflithium plating occurring in the lithium ion battery.

The present disclosure also relates to a method to control a chargingoperation of a lithium ion battery. The method includes measuring one ormore parameters of the lithium ion battery during the chargingoperation. Additionally, the method includes determining a likelihood oflithium plating at an anode based on at least one model relating to thelikelihood of lithium plating at the anode of the lithium ion battery.Further, the at least one model indicates a relationship between the oneor more parameters of the lithium ion battery and the likelihood oflithium plating. Furthermore, the method includes controlling thecharging operation of the lithium ion battery based on the likelihood oflithium plating at the anode.

The present disclosure also relates to a battery module for use in avehicle. The battery module includes a housing, a first terminal, and asecond terminal. The battery module also includes a first batterydisposed in the housing and coupled to the first terminal and the secondterminal. Further, the battery module includes a second battery disposedin the housing, electrically coupled in parallel with the first battery,and electrically coupled to the first terminal and the second terminal.Furthermore, the battery module includes a battery management systemthat monitors one or more parameters of a charging operation of thebattery module, and the battery management system controls the chargingoperation of the second battery based on an indication of a likelihoodof lithium plating generated by at least one lithium plating model ofthe second battery.

DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is perspective view of a vehicle (an xEV) having a battery systemcontributing all or a portion of the power for the vehicle, inaccordance with an embodiment of the present approach;

FIG. 2 is a cutaway schematic view of the xEV of FIG. 1 in the form of ahybrid electric vehicle (HEV), in accordance with an embodiment of thepresent approach;

FIG. 3 is a schematic view of a lithium ion battery system, inaccordance with an embodiment of the present approach;

FIG. 4 is a cutaway view of a lithium ion battery with a spiral woundcell structure, in accordance with an embodiment of the presentapproach;

FIG. 5 is a process flow diagram describing a method for reducing thelikelihood of lithium plating on an anode of a battery based on anelectrochemical model of the battery, in accordance with an embodimentof the present approach; and

FIG. 6 is a process flow diagram describing a method for controllingcharging operations of a battery to reduce lithium plating on an anodeof the battery based on a predictive model and/or an empirical model oflithium plating on the anode of the batter, in accordance with anembodiment of the present approach.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

The battery systems described herein may be used to provide power tovarious types of electric vehicles (xEVs) and other high voltage energystorage/expending applications (e.g., electrical grid power storagesystems). Such battery systems may include one or more battery modules,each battery module having a number of battery cells (e.g., lithium-ion(Li-ion) electrochemical cells) arranged and electrically interconnectedto provide particular voltages and/or currents useful to power, forexample, one or more components of an xEV. As another example, batterymodules in accordance with present embodiments may be incorporated withor provide power to stationary power systems (e.g., non-automotivesystems).

Based on the advantages over traditional gas-power vehicles,manufactures, which generally produce traditional gas-powered vehicles,may desire to utilize improved vehicle technologies (e.g., regenerativebraking technology) within their vehicle lines. Often, thesemanufacturers may utilize one of their traditional vehicle platforms asa starting point. Accordingly, since traditional gas-powered vehiclesare designed to utilize 12 volt battery systems, a 12 volt lithium ionbattery may be used to supplement a 12 volt lead-acid battery. Morespecifically, the 12 volt lithium ion battery may be used to moreefficiently capture electrical energy generated during regenerativebraking and subsequently supply electrical energy to power the vehicle'selectrical system.

As advancements occur with vehicle technologies, high voltage electricaldevices may also be included in the vehicle's electrical system. Forexample, the lithium ion battery may supply electrical energy to anelectric motor in a mild-hybrid vehicle. Often, these high voltageelectrical devices utilize voltage greater than 12 volts, for example,up to 48 volts. Accordingly, in some embodiments, the output voltage ofa 12 volt lithium ion battery may be boosted using a DC-DC converter tosupply power to the high voltage devices. Additionally or alternatively,a 48 volt lithium ion battery may be used to supplement a 12 voltlead-acid battery. More specifically, the 48 volt lithium ion batterymay be used to more efficiently capture electrical energy generatedduring regenerative braking and subsequently supply electrical energy topower the high voltage devices.

Thus, the design choice regarding whether to utilize a 12 volt lithiumion battery or a 48 volt lithium ion battery may depend directly on theelectrical devices included in a particular vehicle. Nevertheless,although the voltage characteristics may differ, the operationalprinciples of a 12 volt lithium ion battery and a 48 volt lithium ionbattery are generally similar. More specifically, as described above,both may be used to capture electrical energy during regenerativebraking and subsequently supply electrical energy to power electricaldevices in the vehicle.

Accordingly, to simplify the following discussion, the presenttechniques will be described in relation to a battery system with a 12volt lithium ion battery and a 12 volt lead-acid battery. However, oneof ordinary skill in art is able to adapt the present techniques toother battery systems, such as a battery system with a 48 volt lithiumion battery and a 12 volt lead-acid battery.

The present disclosure relates to batteries and battery modules. Morespecifically, the present disclosure relates to charging control oflithium ion batteries. Particular embodiments are directed to lithiumion battery cells that may be used in vehicular contexts (e.g., hybridelectric vehicles) as well as other energy storage/expendingapplications (e.g., energy storage for an electrical grid).

More specifically, the present disclosure relates to limiting lithiumplating at anodes of the lithium ion batteries. When a lithium ionbattery charges, it may be advantageous to limit certain chargeparameters to lessen the likelihood of lithium plating at the anodes ofthe lithium ion batteries. To reduce the likelihood of lithium platingwhile still maintaining an efficient charge rate, limits to variouscharge parameters may be dynamically altered to correspond to measuredparameters (e.g., charge current, temperature, or state of charge of thelithium ion battery) presently experienced by the lithium ion battery,which may affect the lithium ion battery's propensity towardexperiencing lithium plating.

With the preceding in mind, the present disclosure describes techniquesfor controlling charging operations of a battery system to prevent thelithium ion batteries from experiencing lithium plating on anodes of thelithium ion batteries. Traditionally, to combat lithium plating, lithiumion battery manufacturers have provided a current limit for chargingoperations of lithium ion batteries. However, these current limits areoften overly conservative for the specific circumstances surrounding alithium ion battery, which may result in inefficient charging operationsby unnecessarily limiting charge current levels. In contrast, a batterymanagement system described in the present disclosure may measureoperating parameters of the lithium ion batteries and control thecharging operations to avoid operating parameter values of the lithiumion batteries that may result in an increased likelihood of lithiumplating on the anodes. More specifically, when a charge current of thelithium ion battery, a temperature of the lithium ion battery, or astate of charge of the lithium ion battery reaches a certain performancelevel that may increase the likelihood of lithium plating, thecontroller may control the charging operation to avoid the certainperformance levels to reduce the likelihood of the lithium plating.Thus, the techniques described herein enable a lithium ion battery toexperience increased reliability and performance.

To help illustrate, FIG. 1 is a perspective view of an embodiment of avehicle 10, which may utilize a regenerative braking system. Althoughthe following discussion is presented in relation to vehicles withregenerative braking systems, the techniques described herein areadaptable to other vehicles that capture/store electrical energy with abattery, which may include electric-powered and gas-powered vehicles.

As discussed above, it would be desirable for a battery system 12 to belargely compatible with traditional vehicle designs. Accordingly, thebattery system 12 may be placed in a location in the vehicle 10 thatwould have housed a traditional battery system. For example, asillustrated, the vehicle 10 may include the battery system 12 positionedsimilarly to a lead-acid battery of a typical combustion-engine vehicle(e.g., under the hood of the vehicle 10). Furthermore, as will bedescribed in more detail below, the battery system 12 may be positionedto facilitate managing temperature of the battery system 12. Forexample, in some embodiments, positioning a battery system 12 under thehood of the vehicle 10 may enable an air duct to channel airflow overthe battery system 12 and cool the battery system 12.

A more detailed view of the battery system 12 is described in FIG. 2. Asdepicted, the battery system 12 includes an energy storage component 14coupled to an ignition system 16, an alternator 18, a vehicle console20, and optionally to an electric motor 22. Generally, the energystorage component 14 may capture/store electrical energy generated inthe vehicle 10 and output electrical energy to power electrical devicesin the vehicle 10.

In other words, the battery system 12 may supply power to components ofthe vehicle's electrical system, which may include radiator coolingfans, climate control systems, electric power steering systems, activesuspension systems, auto park systems, electric oil pumps, electricsuper/turbochargers, electric water pumps, heated windscreen/defrosters,window lift motors, vanity lights, tire pressure monitoring systems,sunroof motor controls, power seats, alarm systems, infotainmentsystems, navigation features, lane departure warning systems, electricparking brakes, external lights, or any combination thereof.Illustratively, in the depicted embodiment, the energy storage component14 supplies power to the vehicle console 20 and the ignition system 16,which may be used to start (e.g., crank) an internal combustion engine24.

Additionally, the energy storage component 14 may capture electricalenergy generated by the alternator 18 and/or the electric motor 22. Insome embodiments, the alternator 18 may generate electrical energy whilethe internal combustion engine 24 is running. More specifically, thealternator 18 may convert the mechanical energy produced by the rotationof the internal combustion engine 24 into electrical energy.Additionally or alternatively, when the vehicle 10 includes an electricmotor 22, the electric motor 22 may generate electrical energy byconverting mechanical energy produced by the movement of the vehicle 10(e.g., rotation of the wheels) into electrical energy. Thus, in someembodiments, the energy storage component 14 may capture electricalenergy generated by the alternator 18 and/or the electric motor 22during regenerative braking. As such, the alternator 18 and/or theelectric motor 22 are generally referred to herein as a regenerativebraking system.

To facilitate capturing and supplying electric energy, the energystorage component 14 may be electrically coupled to the vehicle'selectric system via a bus 26. For example, the bus 26 may enable theenergy storage component 14 to receive electrical energy generated bythe alternator 18 and/or the electric motor 22. Additionally, the bus 26may enable the energy storage component 14 to output electrical energyto the ignition system 16 and/or the vehicle console 20. Accordingly,when a 12 volt battery system 12 is used, the bus 26 may carryelectrical power typically between 8-18 volts.

Additionally, as depicted, the energy storage component 14 may includemultiple battery modules. For example, in the depicted embodiment, theenergy storage component 14 includes a lead acid (e.g., a first) batterymodule 28 in accordance with present embodiments, and a lithium ion(e.g., a second) battery module 30, where each battery module 28, 30includes one or more battery cells. In other embodiments, the energystorage component 14 may include any number of battery modules.Additionally, although the first battery module 28 and the secondbattery module 30 are depicted adjacent to one another, they may bepositioned in different areas around the vehicle. For example, thesecond battery module 30 may be positioned in or about the interior ofthe vehicle 10 while the first battery module 28 may be positioned underthe hood of the vehicle 10.

In some embodiments, the energy storage component 14 may includemultiple battery modules to utilize multiple different batterychemistries. For example, the first battery module 28 may utilize alead-acid battery chemistry and the second battery module 30 may utilizea lithium ion battery chemistry. In such an embodiment, the performanceof the battery system 12 may be improved since the lithium ion batterychemistry generally has a higher coulombic efficiency and/or a higherpower charge acceptance rate (e.g., higher maximum charge current orcharge voltage) than the lead-acid battery chemistry. As such, thecapture, storage, and/or distribution efficiency of the battery system12 may be improved.

To facilitate supply of power from the battery system 12 to the variouscomponents in the vehicle's electrical system (e.g., HVAC system andvehicle console 20), the energy storage component 14 (i.e., batterymodule) includes a first terminal 32 and a second terminal 34. In someembodiments, the second terminal 34 may provide a ground connection andthe first terminal 32 may provide a positive voltage ranging between7-18 volts. A more detailed view of an embodiment of the second batterymodule 30 of the energy storage component 14 illustrating the abovelisted components is depicted in FIG. 3.

As previously noted, the energy storage component 14 may have dimensionscomparable to those of a typical lead-acid battery to limitmodifications to the vehicle 10 design to accommodate the battery system12. For example, the energy storage component 14 may be of similardimensions to an H6 battery, which may be approximately 13.9 inches×6.8inches×7.5 inches. As depicted, the energy storage component 14 may beincluded within a single continuous housing. In other embodiments, theenergy storage component 14 may include multiple housings coupledtogether (e.g., a first housing including the first battery 28 and asecond housing including the second battery 30). In still otherembodiments, as mentioned above, the energy storage component 14 mayinclude the first battery module 28 located under the hood of thevehicle 10, and the second battery module 30 may be located within theinterior of the vehicle 10.

The energy storage component 14 may include the first terminal 32, thesecond terminal 34, a first battery (e.g., a lead acid battery) 28, asecond battery 30 (e.g., a lithium ion battery), and a batterymanagement system 36. As used herein, the battery management system 36generally refers to control components that control operation of thebattery system 12, such as relays within the battery module or switchesin the alternator 18. Additionally, the battery management system 36 maybe disposed within the energy storage component 14, or the batterymanagement system 36 may be remote to the energy storage component 14,as depicted in FIG. 2. The operation of the energy storage component 14may be controlled by the battery management system 36. For example, thebattery management system 36 may regulate an amount of electrical energycaptured/supplied by each battery module 28 or 30 (e.g., to de-rate andre-rate the battery system 12), perform load balancing between thebattery modules 28, 30, control charging and discharging of the batterymodules 28, 30 (e.g., via relays or DC/DC converters), determine a stateof charge of each battery module 28, 30 and/or the entire energy storagecomponent 14, activate an active cooling mechanism, activate a shortcircuit protection system, and the like.

Accordingly, the battery management system 36 may include a memory 38and a processor 40 programmed to execute control algorithms forperforming such tasks. More specifically, the processor 40 may includeone or more application specific integrated circuits (ASICs), one ormore field programmable gate arrays (FPGAs), one or more general purposeprocessors, or any combination thereof. Additionally, the memory 38 mayinclude volatile memory, such as random access memory (RAM), and/ornon-volatile memory, such as read-only memory (ROM), optical drives,hard disc drives, or solid-state drives. In some embodiments, thebattery management system 36 may include portions of a vehicle controlunit (VCU) and/or a separate battery control module. Additionally, asdepicted, the battery management system 36 may be included separate fromthe energy storage component 14, such as a standalone module. In otherembodiments, the battery management system 36 may be included within theenergy storage component 14.

Further, the battery management system 36 may interact with sensorscoupled to the energy storage component 14. For example, the batterymanagement system 36 may receive a temperature indication from atemperature sensor 42 coupled to the energy storage component 14. Thebattery management system 36 may also measure current and voltageapplied to or withdrawn from the energy storage component 14.

Additionally, as depicted in FIG. 2, the first battery 28 and the secondbattery 30 are connected in parallel across the first terminal 32 andthe second terminal 34 to enable charging and discharging of thebatteries. As described above, the battery terminals 32 and 34 mayoutput the power stored in the energy storage component 14 to providepower to the vehicle's electrical system. Further, the battery terminals32 and 34 may also input power to the energy storage component 14 toenable the first battery 28 and the second battery 30 to charge, forexample, when the alternator 18 generates electrical power throughregenerative braking.

To provide more detail as to the energy storage component 14, FIG. 3illustrates a schematic view of components of the second battery 30. Asmentioned above in the discussion of FIG. 2, the second battery 30 mayutilize a lithium ion chemistry. Accordingly, the second battery 30 isillustrated as a lithium ion battery in FIG. 3. The second battery 30may include the first terminal 32 coupled at an anode 44 and the secondterminal 34 coupled at a cathode 46. Additionally, the anode 44 may bemade from carbon (e.g., graphite), silicon, silicon dioxide, or anyother suitable material. Further, the cathode 46 may be made fromcobalt, manganese, nickel-cobalt manganese, aluminum, or any othersuitable material. The anode 44 and the cathode 46 may be separated by aseparator 48. The separator 48 may be a polypropylene or polyethylenematerial that provides electrical separation between the anode 44 andthe cathode 46 while allowing charged lithium ions 52 to pass through inan unobstructed manner.

During a charging operation of the second battery 30, an electriccurrent 49 is applied to the second terminal 34 toward the cathode 46.The charging operation may use power generated by the internalcombustion engine 24 or power generated by regenerative braking torecharge the second battery 30. Further, as the electric current 49flows toward the second terminal 34, electrons 50 flow toward the firstterminal 32 and the anode 44. In this manner, the electrons 50 enteringthe anode 44 attract the positively charged lithium ions 52 in such amanner that drives the lithium ions 52 from the cathode 46, through theseparator 48, and to the anode 44 along a path 54. As the lithium ions52 travel to the anode 44 along the path 54, a state of charge of thesecond battery 30 also increases.

To control charging of the second battery 30, the battery managementsystem 36 may receive inputs from sensors and may control application ofpower from the alternator 18 to the cathode 46. For example, undercertain conditions, lithium plating may occur on the anode 44 at aninterface between the anode 44 and the separator 48 as the lithium ions52 are deposited on the material that makes up the anode 44. Forinstance, charging the second battery 30 at −40 degrees Celsius mayresult in a heightened likelihood of lithium plating on the anode 44.Lithium plating may result in battery degradation as the lithium ions 52deposited on the anode 44 effectively remove active lithium ions 52 fromfuture electrochemical reactions within the second battery 30.Accordingly, a lifespan of the battery 30 may be significantly reduceddue to lithium plating on the anode 44 during charging operations.Therefore, it may be desirable to avoid the certain conditions thatresult in a greater likelihood of lithium plating on the anode 44 bycontrolling the application of power from the alternator 18 to thecathode 46 during regenerative braking or when the alternator 18converts mechanical movement of the internal combustion engine 24 intoelectrical power to charge the energy storage component 14.

To facilitate the aforementioned control, the second battery 30 mayinclude the temperature sensor 42 and/or additional sensors 56. Theadditional sensors 56 may measure, for example, voltage and/or current49 applied at the second terminal 34. In general, several factors mayinfluence lithium plating on the anode 44. For example, as a state ofcharge of the second battery 30 increases, a likelihood of lithiumplating also increases. Similarly, as the state of charge of the secondbattery 30 decreases, the likelihood of lithium plating decreases.Additionally, greater current levels applied to the second battery 30may increase the likelihood of lithium plating, a decrease in voltage atan interface between the separator 48 and the anode 44 may increase thelikelihood of lithium plating, and a decrease in temperature of thesecond battery 30 may also increase the likelihood of lithium plating.Accordingly, the battery management system 36 may control theapplication of power by the alternator 18 to the second battery 30 in anumber of ways to limit the likelihood of lithium plating on the anode44 in view of the factors described above.

For example, the current 49 applied during a charging operation may belimited to different levels depending on the state of charge of thesecond battery 30, the temperature of the second battery 30, a durationand/or frequency of charging pulses applied to the battery 30, or anyother factor that may influence the likelihood of lithium plating on theanode 44. Because these conditions may change over time, the batterymanagement system 36 may dynamically control the power output of thealternator 18 into the second battery 30 during the charging operation.Therefore, the likelihood of the anode 44 experiencing lithium platingmay not correspond to a specific level of the current 49. Rather, thelikelihood of lithium plating at a specific level of the current 49 mayvary based on the various factors discussed above.

Turning now to FIG. 4, a cutaway view of the second battery 30 with aspiral wound cell structure is illustrated. The second battery 30 mayinclude the anode 44 and the cathode 46 separated by the separator 48and wrapped in a spiral wound configuration within the second battery30. Additionally, the second terminal 34 may electrically couple to thecathode 46 and the first terminal 32 may electrically couple to theanode 44. Accordingly, the spiral wound configuration of the secondbattery 30 depicted in FIG. 4 may couple to the alternator 18 and thebattery management system 36 in a similar manner to the schematicrepresentation of the second battery 30 depicted in FIG. 3. Further,during a recharge operation of the second battery 30, the lithium ions52 may move from the cathode 46, through the separator 48, and to theanode 44 in a manner similar to the schematic representation of FIG. 3.Furthermore, it may be appreciated that in the spiral woundconfiguration, the anode 44 and the cathode 46 may generally be disposedwithin the second battery 30 in a configuration that is parallel to theseparator 48.

To illustrate the functionality of the battery management system 36,FIG. 5 is a process flow diagram describing a method 60 for controllingcharging operations using an electrochemical model 61 of the secondbattery 30. Initially, at block 62, an electrochemical model 61 of thesecond battery 30 may be generated. The electrochemical model 61 of thesecond battery 30 may estimate a voltage between the separator 48 andthe anode 44. As the voltage between the separator 48 and the anode 44decreases, the likelihood that lithium plating will occur on the anode44 increases. The estimated voltage value may generally include thenegative voltage of the second battery 30 instead of the entire voltagepotential of the battery. The electrochemical model 61 of the secondbattery 30 may determine the negative voltage at which plating is likelyto occur on the anode 44 based on factors such as charging current andtemperature. By way of example, the electrochemical model 61 may be anextensive mathematical model that solves for dependent variables, suchas electrolyte concentration, electrolyte potential, solidconcentration, solid potential, reaction rate, local current density,etc., using governing equations based on porous electrode theory andconcentrated electrolyte theory. Further, the electrochemical model 61may generally approximate an energy balance depicted by the followingequation:

$\begin{matrix}{{\epsilon\frac{\partial c}{\partial t}} = {{{\nabla\epsilon^{1.5}}{D\left( {1 - \frac{d\mspace{11mu}\ln\mspace{11mu} c_{0}}{d\mspace{11mu}\ln\mspace{11mu} c}} \right)}{\nabla c}} + \frac{{t_{-}^{0}{\nabla i_{2}}} + {i_{2}{\nabla t_{-}^{0}}}}{z_{+}v_{+}F} - {\nabla{cv}_{0}} + {aj}_{-}}} & (1)\end{matrix}$where ϵ is a volume fraction of electrolyte within the second battery30, c is salt concentration in the electrolyte, t is time, D is a saltdiffusion coefficient, t⁰ is a transference number of species withrespect to solvent velocity, i₂ is a transfer current density normal tothe surface of an active material, z is an ion change, v is adifferential volume element, F is Faraday's constant, and j is a flux ofspecies normal to the electrode interface due to the electrochemicalreaction. However, approximating equation 1 with the electrochemicalmodel 61 may have a high computation cost.

Accordingly, at block 64, a reduced order model 63 of theelectrochemical model for the second battery 30 may be generated toreduce the computation cost. For example, the electrochemical model 61may be generated but only used to obtain the reduced order model 63,which may be employed for determining conditions that may increase thelikelihood of lithium plating to avoid such conditions at the secondbattery 30. The reduced order model 63 may decrease computationalcomplexity of the electrochemical model 61 for the second battery 30.For example, the reduced order model 63 may reduce state spacedimensions or degrees of freedom of the electrochemical model 61 toprovide a computationally efficient alternative to the electrochemicalmodel 61. Additionally, or alternatively, a look-up table 65 or anequivalent circuit model 67 (e.g., a circuit model that substituteselectrical characteristics of a circuit of the second battery 30)relating to the electrochemical model 61 for the second battery 30 mayalso be generated and stored in the memory 38 of the battery managementsystem 36. The reduced order model 63, the look-up table 65, and theequivalent circuit model 67 may decrease computation cost by reducingthe complexity of the electrochemical model 61. Accordingly, a time costfor dynamically changing charging parameters may also be reduced. Thereduced order model 63 of the electrochemical model 61 for the secondbattery 30 may be in the form:

$\;{{{\overset{\_}{J}}_{s}(t)} = \begin{matrix}\left\{ \begin{matrix}{{a_{n}{i_{0,s}\left\lbrack {{\exp\left( {\frac{\alpha_{a,s}F}{R_{g}T}{{\overset{\_}{\eta}}_{s,{oc}}(t)}} \right)} - {\exp\left( {{- \frac{\alpha_{c,s}F}{R_{g}T}}{{\overset{\_}{\eta}}_{s,{oc}}(t)}} \right)}} \right\rbrack}},{x_{0} < L_{n}}} \\{0,{x_{0} = L_{n}}}\end{matrix} \right. & (2)\end{matrix}}$where J _(s)(t) is a measure of a rate of irreversible lithium loss dueto lithium plating, a_(n) is a surface area of a porous electrode,i_(0,s) is an exchange current density for an intercalation reaction,α_(a,s) is an anodic coefficient of the electrochemical reaction, F isFaraday's constant, R_(g) is a particle radius, T is temperature, η_(s,oc)(t) is a local overpotential that drives the electrochemicalreaction, α_(c,s) is a cathodic coefficient of the electrochemicalreaction, x₀ is a length dimension, and L_(n) is the length of a cell orelectrode. The reduced order model 63 provided by equation 2 yields analgebraic solution rather than a differential solution of the lithiumplating likelihood. Accordingly, implementing the reduced order model 63over the electrochemical model 61 may result in increased processingefficiency when determining a likelihood of lithium plating.

Further, the look-up table 65 may relate various measurable factors ofthe second battery 30 to determine the likelihood of lithium plating atthe anode 44 based on the electrochemical model 61 of the second battery30. For example, the look-up table 65 may provide a mechanism forrelating the temperature of the second battery 30 and the current 49 ofthe charging operation to the likelihood of lithium plating.Accordingly, the look-up table 65 may enable the battery managementsystem 36 to estimate a likelihood of lithium plating on the anode 44based on the electrochemical model 61.

Furthermore, the equivalent circuit model 67 may provide a simplifiedrepresentation of the second battery 30. For example, the equivalentcircuit model 67 may be represented in the form:

$\begin{matrix}{V_{k} = {K_{0} - \frac{K_{1}}{z_{k}} + {K_{3}{\ln\left( z_{k} \right)}} + {K_{4}{\ln\left( {1 - z_{k}} \right)}} - {R_{0}I_{k}}}} & (3)\end{matrix}$where V_(k) is a terminal voltage of the second battery 30, z_(k) is astate of charge of the second battery 30, I_(k) is a charge current ofthe second battery 30, K_(1 . . . 4) are parameters for a dependencebetween an open circuit voltage of the second battery 30 and the stateof charge, and R₀ is an internal ohmic resistance that depends on adirection of current flow. Similar to the reduced order model 63, theequivalent circuit model 67 yields an algebraic solution, which mayincrease processing efficiency when determining the likelihood oflithium plating.

For example, at block 66, measurable factors of the second battery 30may be applied to the reduced order model 63, the look-up table 65,and/or the equivalent circuit model 67. In this manner, the simplifiedmodels may provide an indication to the battery management system 36 ofthe likelihood of lithium plating on the anode 44. For example, thereduced order model 63, the look-up table 65, and the equivalent circuitmodel 67 may each provide an indication, based on an estimated voltageat the interface between the separator 48 and the anode 44, of whetherthe lithium plating is likely to occur.

Subsequently, at block 68, charging operations may be controlled by thebattery management system 36 based on the determined lithium platinglikelihood. For example, the battery management system 36 may controlthe alternator 18 to reduce the current 49 entering the cathode 46 ofthe second battery 30 to reduce the likelihood of lithium plating whenthe measurable factors of the second battery 30 indicate that thelikelihood of lithium plating is above a threshold. Additionally, thebattery management system 36 may limit the pulse duration of thecharging operation to reduce the likelihood of lithium plating when themeasurable factors of the second battery 30 indicate that the likelihoodof lithium plating is above a threshold. The threshold for thelikelihood of lithium plating may, for example, be when the likelihoodof lithium plating is greater than 50 percent.

In another embodiment, FIG. 6 is a process flow diagram describing amethod 80 for controlling charging operations of a battery to reducelithium plating on an anode of the battery based on a predictive modelincluding a physical model 83 and/or an empirical model 85 of lithiumplating on the anode 44 of the second battery 30. Initially, at block82, cell voltage, current, and temperature of the second battery 30 maybe observed over time during a charging operation. Additionally, in someembodiments, other additional parameters related to the second battery30 and the charging operation, such as cell state of charge, cell age,charge pulse duration, etc., may also be observed.

After observing effects of the above referenced parameters on the secondbattery 30 over a period of time, at block 84, a lithium platingphysical model 83 and/or a lithium plating empirical model 85 may begenerated based on the observations. The lithium plating physical model83 may, for example, be a physical model 83 of lithium precipitation andgrowth that predicts lithium plating as a function of potential on theanode 44. Accordingly, the physical model 83 may relate the cell voltagemeasurements, current measurements, and temperature measurements of thesecond battery 30 at a specific time to determine a likelihood oflithium plating on the anode 44 at the specific time. For example, thephysical model 83 may be represented by the following general equation:Probability of Lithium Plating=f[Rate of lithiumprecipitation(Anode(I(t)&V(t)),lithium diffusionrate(SOC),Rest(t),temperature (t),aging(t)],t:time  (4)The likelihood of lithium plating may be calculated through establishingthe physical model 83 as a function of: a rate of lithium precipitation,which is a function of anode voltage, current, and time; a lithiumdiffusion rate in the anode 44, which is a function of the state ofcharge (SOC) of the second battery 30; a resting time; a temperature ofthe second battery 30; and battery aging conditions. Parameters andfunctions of the physical model 83 may be developed from full cell, halfcell, and various electrochemical (e.g., AC impedance and/orGalvanostatic Intermittent Titration Technique (GITT)) testing data ofthe second battery 30.

Additionally, the empirical model 85 may, for example, trackampere-seconds (A-s) of the current 49 applied during a chargingoperation when the potential at the anode 44 indicates an increasedlikelihood of lithium plating on the anode 44. For example, theempirical model 85 may indicate that a certain amount of ampere-secondsapplied to the second battery 30 within a certain time period may resultin an increased likelihood of lithium plating on the anode 44.Additionally, the temperature of the second battery 30 and the voltageapplied to the second battery 30 may also influence the certain amountof ampere-seconds that may increase the likelihood of lithium plating.By tracking the ampere-seconds of the current 49, along with thetemperature and voltage, the empirical model 85 may enable the batterymanagement system 36 to track when the likelihood of lithium platingincreases.

Similarly, another empirical model 85 may classify the likelihood oflithium plating as a function of a magnitude of the current 49 appliedduring a charging operation, the potential at the anode 44, and time.Accordingly, the empirical model 85 may be generated by observinglithium plating over time based on various battery conditions during acharging operation to provide a model for the likelihood of lithiumplating at the anode 44. In this empirical model 85, the batterymanagement system 36 may track the magnitude of the current 49 to make adetermination as to the likelihood of lithium plating at the anode 44based on the magnitude of the current 49.

By way of example, the empirical model 85 may be represented by thefollowing general equation:Probability of Lithium Plating=f[CellI(t),CellV(t),CellTemperature(t),Cell SOC(t),aging(t)],t:time  (5)The likelihood of lithium plating may be calculated from an empiricallydeveloped function which applies a cell current profile, cell voltage,cell temperature, cell SOC, and battery aging conditions to thelikelihood of lithium plating at the anode 44. The empirically developedfunction may include polynomial functions or the empirically developedfunction may be generated from look-up data, which is developed orderived from the physical model 83 or design of experiments (DOE)experimental data.

After generating a physical model 83 and/or an empirical model 85, atblock 86 present conditions of the second battery 30 may be measured. Bymeasuring the present conditions of the second battery 30, at block 88,the battery management system 36 may determine present lithium platingprobabilities based on the present conditions of the second battery 30using the physical model 83 and/or the empirical model 85. Additionally,in some instances both a physical model 83 and an empirical model 85 maybe used in determining the lithium plating probabilities on the anode44. For example, the physical model 83 and the empirical model 85 maygenerally be less accurate than the electrochemical model 61 describedin relation to the method 60 of FIG. 5. However, the physical model 83and the empirical model 85 may each use significantly less computationalpower than the electrochemical model 61. Accordingly, in somesituations, the battery management system 36 may assign an accuracyfactor to each of the physical model 83 and the empirical model 85 todetermine which model to use for a specific situation. For example, thephysical model 83 may be more accurate at low temperatures (e.g., duringwinter months), while the empirical model 85 may be more accurate whilethe second battery 30 experiences warmer temperatures. Accordingly, thebattery management system 36 may select between the two models based onmeasured conditions and known strengths of the physical and empiricalmodels 83 and 85 (e.g., based on accuracy factors of the models underspecific conditions).

Subsequently, at block 90, the battery management system 36 may controlcharging operations based on the lithium plating likelihood determinedfrom either or both of the empirical model 85 and the physical model 83.For example, if the models indicate that there is a high likelihood oflithium plating under present charging conditions of the second battery30, the battery management system 36 may, for example, control thealternator 18 to output the current 49 at a lower level. Likewise, insome situations, the battery management system 36 may control thealternator 18 to decrease charge pulse durations that are applied to thesecond battery 30 when the battery management system 36 detects anincreased likelihood of lithium plating on the anode 44. It may beappreciated that the electrochemical model 61, the reduced order model63, the look-up table 65, the equivalent circuit model 67, the physicalmodel 83, the empirical model 85, and any other model related to lithiumplating may all generally be defined as lithium plaiting models in thecontext of this disclosure.

In some instances, the likelihood of lithium plating may be determinedto be greater than a threshold value when the likelihood of lithiumplating is greater than 50 percent. Additionally, in other instances,the likelihood of lithium plating may be determined to be greater thanthe threshold value when the likelihood is greater than approximately 70percent, 75 percent, or 80 percent under the present charging operationconditions. Further, any other method of altering the chargingoperations that results in a reduction in the likelihood of lithiumplating may also be employed by the battery management system 36 upondetermining that the likelihood of lithium plating is above thethreshold value.

One or more of the disclosed embodiments, alone or on combination, mayprovide one or more technical effects including decreasing thelikelihood of lithium plating on the anode 44 of the second battery 30.The technical effects and technical problems in the specification areexemplary and are not limiting. It should be noted that the embodimentsdescribed in the specification may have other technical effects and cansolve other technical problems.

While only certain features and embodiments have been illustrated anddescribed, many modifications and changes may occur to those skilled inthe art (e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters (e.g.,temperatures, pressures, etc.), mounting arrangements, use of materials,colors, orientations, etc.) without materially departing from the novelteachings and advantages of the disclosed subject matter. The order orsequence of any process or method steps may be varied or re-sequencedaccording to alternative embodiments. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the disclosure.Furthermore, in an effort to provide a concise description of theexemplary embodiments, all features of an actual implementation may nothave been described. It should be appreciated that in the development ofany such actual implementation, as in any engineering or design project,numerous implementation specific decisions may be made. Such adevelopment effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure, without undue experimentation.

The invention claimed is:
 1. A battery system, comprising: a lithium ionbattery configured to couple to an electrical system; and a batterymanagement system configured to electrically couple to the lithium ionbattery and configured to control one or more recharge operations of thelithium ion battery based on a plurality of lithium plating models andone or more monitored parameters, wherein the plurality of lithiumplating models is indicative of a relationship between the one or moremonitored parameters and a likelihood of lithium plating occurring inthe lithium ion battery, and wherein the plurality of lithium platingmodels comprises a physical model and an empirical model related tolithium plating at an anode of the lithium ion battery; wherein thebattery management system is configured to: monitor the one or moremonitored parameters of the lithium ion battery; assign one or moreaccuracy factors to the physical model and the empirical model based ona temperature associated with the lithium ion battery; determine whichof the physical model, the empirical model, or both to use as a triggerto control the one or more recharge operations of the lithium ionbattery based on the one or more accuracy factors in view of the one ormore monitored parameters; and control the one or more rechargeoperations of the lithium ion battery based on the trigger, theplurality of lithium plating models, and the one or more monitoredparameters.
 2. The battery system of claim 1, wherein the batterymanagement system is configured to control an alternator to control theone or more recharge operations of the lithium ion battery.
 3. Thebattery system of claim 1, wherein the one or more monitored parametersof the lithium ion battery comprise charge current, the temperature,state of charge, charging pulse duration, cell age, resting time, or anycombination thereof.
 4. The battery system of claim 1, wherein theplurality of lithium plating models comprises a reduced orderelectrochemical model of the lithium ion battery.
 5. The battery systemof claim 1, wherein the physical model or the empirical model isconfigured to provide an indication of the likelihood of the lithiumplating occurring at the anode.
 6. The battery system of claim 5,wherein the physical model or the empirical model is generated based onone or more effects of the one or more recharge operations on thelithium ion battery over time.
 7. The battery system of claim 1, whereinat least one lithium plating model of the plurality of lithium platingmodels is influenced by a battery temperature of the lithium ionbattery.
 8. The battery system of claim 1, wherein the lithium ionbattery is configured to electrically couple in parallel to a lead-acidbattery within a single housing.
 9. A method to control a chargingoperation of a lithium ion battery, comprising: measuring, via aprocessor, one or more parameters of the lithium ion battery during thecharging operation; determining, via the processor, a likelihood oflithium plating at an anode based on a plurality of models relating tothe likelihood of lithium plating at the anode of the lithium ionbattery, wherein the plurality of models indicates a relationshipbetween the one or more parameters of the lithium ion battery and thelikelihood of lithium plating, wherein the plurality of lithium platingmodels is indicative of a relationship between the one or moreparameters and the likelihood of lithium plating occurring in thelithium ion battery, and wherein the plurality of lithium plating modelscomprises a physical model and an empirical model related to lithiumplating at the anode of the lithium ion battery; and controlling, viathe processor, the charging operation of the lithium ion battery basedon the likelihood of lithium plating at the anode, wherein controllingthe charging operation of the lithium battery comprises: assigning, viathe processor, one or more accuracy factors to the physical model andthe empirical model based on a temperature associated with the lithiumion battery; determining, via the processor, which of the physicalmodel, the empirical model, or both to use as a trigger to control thecharging operation of the lithium ion battery based on the one or moreaccuracy factors in view of the one or more parameters; and controlling,via the processor, the charging operation of the lithium ion batterybased on the trigger, the plurality of lithium plating models, and theone or more parameters.
 10. The method of claim 9, comprising: observingcell voltage, current, and the temperature of the lithium ion batteryduring the charging operation; and generating at least one model of theplurality of models based on one or more effects of the cell voltage,the current, and the temperature during the charging operation on thelithium plating at the anode.
 11. The method of claim 10, wherein thephysical model relates observed physical characteristics of the lithiumion battery to the likelihood of lithium plating, and wherein theempirical model relates the cell voltage, the current, and thetemperature observed over time to the likelihood of lithium plating. 12.The method of claim 9, wherein at least one model of the plurality ofmodels comprises a reduced order electrochemical model of the lithiumion battery configured to reduce computational complexity of anelectrochemical model of the lithium ion battery.
 13. The method ofclaim 9, wherein at least one model of the plurality of models isrepresented as a look-up table.
 14. A battery module for use in avehicle, comprising: a housing; a first terminal and a second terminal;a first battery disposed in the housing and configured to couple to thefirst terminal and the second terminal; a second battery disposed in thehousing, electrically coupled in parallel with the first battery, andconfigured to electrically couple to the first terminal and the secondterminal; a battery management system configured to monitor one or moreparameters of a charging operation of the battery module, and to controlthe charging operation of the second battery based on based on aplurality of lithium plating models and one or more monitoredparameters, wherein the plurality of lithium plating models isindicative of a relationship between the one or more parameters and alikelihood of lithium plating occurring in the second battery, andwherein the plurality of lithium plating models comprises a physicalmodel and an empirical model related to lithium plating at an anode ofthe second battery, and wherein the battery management system isconfigured to: monitor the one or more parameters of the lithium ionbattery; assign one or more accuracy factors to the physical model andthe empirical model based on a temperature associated with the secondbattery; determine which of the physical model, the empirical model, orboth to use as a trigger to control the charging operation of the secondbattery based on the one or more accuracy factors in view of the one ormore parameters; and control the charging operation of the secondbattery based on the trigger, the plurality of lithium plating models,and the one or more monitored parameters.
 15. The battery module ofclaim 14, wherein the plurality of lithium plating models comprises anelectrochemical model of the second battery, wherein the electrochemicalmodel estimates a voltage between a separator and an anode of the secondbattery.
 16. The battery module of claim 14, wherein the plurality oflithium plating models comprises a predictive model of the secondbattery, and wherein the predictive model of the second batterycomprises the physical model that relates observed physicalcharacteristics of the second battery to the likelihood of lithiumplating in the second battery and the empirical model of the secondbattery that relates measured parameters of the second battery over timeto the likelihood of lithium plating in the second battery.
 17. Thebattery module of claim 14, wherein the battery management system isconfigured to control the charging operation by reducing a chargecurrent applied to the second battery by an alternator.
 18. The batterymodule of claim 14, wherein the charging operation is configured to usepower generated through regenerative breaking to charge the firstbattery and the second battery.